Multiple clear cell trichoblastoma.

Clear cell trichoblastoma is a very rare neoplasm with follicular differentiation described recently. Only three cases of clear cell trichoblastoma were reported in literature and all of them were presented as single lesion. Here, we report a case of clear cell trichoblastoma with multiple lesions in a child. Two biopsies from the patient showed that the neoplasm was located in the dermis, and step sections showed that they were connected with the follicular infundibulum. The neoplasm was almost made of clear cells that had clear cytoplasm and eccentrically disposed nucleus. At the periphery of the neoplasm, the clear cells showed palisade array with the nucleus at the pole opposite the thick basement membrane, and only a few basal cells were located at the periphery of the neoplasm. Periodic acid-Schiff stain was almost negative in the clear cells. Immunohistochemistry studies showed the neoplasm stained positive for AE1/AE3 but negative for CAM 5.2, cytokeratin 7, cytokeratin 20, epithelia antigen, carcinoembryonic antigen, epithelial membrane antigen, androgen receptor, S-100 and CD34. The clinical and histopathological characters suggested the diagnosis of multiple clear cell trichoblastoma. After 20 months' follow up, the lesions of the patient showed incomplete regression, which is a rare phenomenon in neoplasm with follicular differentiation.